When digital information is recorded on high-density magnetic recording media (tape, disk, etc.) it must be encoded in such a manner as to be reliably played back. Various encoding techniques have been developed and are well known to those skilled in the art. One of the more efficient encoding methods is modified phase modulation, also known as MFM. Hereinafter, this encoding method will be referred to as MFM encoding MFM encoding is usually implemented by employing a variety of random logic devices.
Further, when digital information is recorded on a magnetic disk, bit shifting can occur as recorded flux reversals move from denser toward less dense regions of the track. Movement is apparent, not real; it is actually a time displacement caused by characteristics of the magnetic medium. A technique known as write precompensation has been developed, and is well known by those skilled in the art, which counteracts this read data bit shift with an equivalent, but opposite, time shift on the write bit data stream. Write precompensation is usually implemented by using analog or digital delays.